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The GALEX View of Supernova Hosts 星系望远镜对超新星宿主的观测
arXiv: Astrophysics Pub Date : 2008-12-22 DOI: 10.1063/1.3141604
J. Neill, M. Sullivan, M. D. W. U. O. Technology, U. Oxford, C. Observatories
{"title":"The GALEX View of Supernova Hosts","authors":"J. Neill, M. Sullivan, M. D. W. U. O. Technology, U. Oxford, C. Observatories","doi":"10.1063/1.3141604","DOIUrl":"https://doi.org/10.1063/1.3141604","url":null,"abstract":"We exploit the accumulating, high‐quality, multi‐wavelength imaging data of nearby supernova (SN) hosts to explore the relationship between SN production and host galaxy evolution. The Galaxy Evolution Explorer (GALEX, [1]) provides ultraviolet (UV) imaging in two bands, complementing data in the optical and infra‐red (IR). We compare host properties, derived from spectral energy distribution (SED) fitting, with nearby, well‐observed SN Ia light curve properties. We also explore where the hosts of different types of SNe fall relative to the red and blue sequences on the galaxy UV‐optical color‐magnitude diagram (CMD, [2]). We conclude that further exploration and larger samples will provide useful results for constraining the progenitors of SNe.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85798475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Efficiency of Neutrino Annihilation around Spinning Black Holes 旋转黑洞周围中微子湮灭的效率
arXiv: Astrophysics Pub Date : 2008-12-21 DOI: 10.1063/1.3155863
I. Zalamea, A. Beloborodov
{"title":"Efficiency of Neutrino Annihilation around Spinning Black Holes","authors":"I. Zalamea, A. Beloborodov","doi":"10.1063/1.3155863","DOIUrl":"https://doi.org/10.1063/1.3155863","url":null,"abstract":"A fraction of neutrino emission from GRB accretion disks annihilates above the disk, creating e± plasma that can drive GRB explosions. We calculate the efficiency of this annihilation using the recent detailed model of hyper‐accretion disks around Kerr black holes. Our calculation is fully relativistic and based on a geodesic‐tracing method. We find that the efficiency is a well‐defined function of (1) accretion rate and (2) spin of the black hole. It is practically independent of the details of neutrino transport in the opaque zone of the disk. The results help identify the accretion disks whose neutrino emission can power GRBs.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85866070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 3
Curious Variables Experiment (CURVE). CCD photometry of active dwarf nova DI UMa 好奇变量实验(CURVE)。活动矮新星DI UMa的CCD光度测定
arXiv: Astrophysics Pub Date : 2008-12-21 DOI: 10.1051/0004-6361/200811256
A. Rutkowski, A. Olech, M. Wi'sniewski, P. Pietrukowicz, J. Pala, Radosław Poleski
{"title":"Curious Variables Experiment (CURVE). CCD photometry of active dwarf nova DI UMa","authors":"A. Rutkowski, A. Olech, M. Wi'sniewski, P. Pietrukowicz, J. Pala, Radosław Poleski","doi":"10.1051/0004-6361/200811256","DOIUrl":"https://doi.org/10.1051/0004-6361/200811256","url":null,"abstract":"We report an analysis of photometric behaviour of DI UMa, an extremely active dwarf nova. The observational campaign (completed in 2007) covers five superoutbursts and four normal outbursts. We examined principal parameters of the system to understand peculiarities of DI UMa, and other active cataclysmic variables. Based on precise photometric measurements, temporal light curve behaviour, O-C analysis, and power spectrum analysis, we investigated physical parameters of the system. We found that the period of the supercycle now equals 31.45 +/-0.3 days. Observations during superoutbursts infer that the period of superhumps equals P_sh = 0.055318(11) days (79.66 +/- 0.02 min). During quiescence, the light curve reveals a modulation of period P_orb = 0.054579(6) days (78.59 +/- 0.01 min), which we interpret as the orbital period of the binary system. The values obtained allowed us to determine a fractional period excess of 1.35% +/- 0.02%, which is surprisingly small compared to the usual value for dwarf novae (2%-5%). A detailed O-C analysis was performed for two superoutbursts with the most comprehensive coverage. In both cases, we detected an increase in the superhump period with a mean rate of dot_P/P_sh = 4.4(1.0)*10^{-5}. Based on these measurements, we confirm that DI UMa is probably a period bouncer, an old system that reached its period minimum a long time ago, has a secondary that became a degenerate brown dwarf, the entire system evolving now toward longer periods. DI UMa is an extremely interesting object because we know only one more active ER UMa star with similar characteristics (IX Dra).","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86222816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 9
The Magellanic System: What have we learnt from FUSE? 麦哲伦星系:我们从FUSE中学到了什么?
arXiv: Astrophysics Pub Date : 2008-12-20 DOI: 10.1063/1.3154068
N. Lehner
{"title":"The Magellanic System: What have we learnt from FUSE?","authors":"N. Lehner","doi":"10.1063/1.3154068","DOIUrl":"https://doi.org/10.1063/1.3154068","url":null,"abstract":"I review some of the findings on the Magellanic System produced by the Far Ultraviolet Spectroscopic Explorer (FUSE) during and after its eight years of service. The Magellanic System with its high‐velocity complexes provides a nearby laboratory that can be used to characterize phenomena that involve interaction between galaxies, infall and outflow of gas and metals in galaxies. These processes are crucial for understanding the evolution of galaxies and the intergalactic medium. Among the FUSE successes I highlight are the coronal gas about the LMC and SMC, and beyond in the Stream, the outflows from these galaxies, the discovery of molecules in the diffuse gas of the Stream and the Bridge, an extremely sub‐solar and sub‐SMC metallicity of the Bridge, and a high‐velocity complex between the Milky Way and the Clouds.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76967396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
MOJAVE: Monitoring of Jets in AGN with VLBA Experiments. V. Multi-epoch VLBA Images 用VLBA实验监测AGN中的射流。V.多历元VLBA图像
arXiv: Astrophysics Pub Date : 2008-12-20 DOI: 10.1088/0004-6256/137/3/3718
M. Lister, H. Aller, M. Aller, M. Cohen, D. Homan, M. Kadler, K. Kellermann, Y. Y. Kovalev, E. Ros, T. Savolainen, J. Zensus, R. Vermeulen
{"title":"MOJAVE: Monitoring of Jets in AGN with VLBA Experiments. V. Multi-epoch VLBA Images","authors":"M. Lister, H. Aller, M. Aller, M. Cohen, D. Homan, M. Kadler, K. Kellermann, Y. Y. Kovalev, E. Ros, T. Savolainen, J. Zensus, R. Vermeulen","doi":"10.1088/0004-6256/137/3/3718","DOIUrl":"https://doi.org/10.1088/0004-6256/137/3/3718","url":null,"abstract":"We present images from a long term program (MOJAVE: Monitoring of Jets in AGN with VLBA Experiments) to survey the structure and evolution of parsec-scale jet phenomena associated with bright radio-loud active galaxies in the northern sky. The observations consist of 2424 15 GHz VLBA images of a complete flux-density limited sample of 135 AGN above declination -20 degrees, spanning the period 1994 August to 2007 September. These data were acquired as part of the MOJAVE and 2 cm Survey programs, and from the VLBA archive. The sample selection criteria are based on multi-epoch parsec-scale (VLBA) flux density, and heavily favor highly variable and compact blazars. The sample includes nearly all the most prominent blazars in the northern sky, and is well-suited for statistical analysis and comparison with studies at other wavelengths. Our multi-epoch and stacked-epoch images show 94% of the sample to have apparent one-sided jet morphologies, most likely due to the effects of relativistic beaming. Of the remaining sources, five have two-sided parsec-scale jets, and three are effectively unresolved by the VLBA at 15 GHz, with essentially all of the flux density contained within a few tenths of a milliarcsecond.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83009221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 137
Morphology and hardness ratio exploitation under limited statistics 在有限的统计条件下进行形貌和硬度比的开发
arXiv: Astrophysics Pub Date : 2008-12-19 DOI: 10.1063/1.3076767
A. Clapson, M. Dyrda, D. Nekrassov, M. Renaud
{"title":"Morphology and hardness ratio exploitation under limited statistics","authors":"A. Clapson, M. Dyrda, D. Nekrassov, M. Renaud","doi":"10.1063/1.3076767","DOIUrl":"https://doi.org/10.1063/1.3076767","url":null,"abstract":"{gamma}-ray astronomy has produced for several years now sky maps for low photon statistics, non-negligible background and comparatively poor angular resolution. Quantifying the significance of spatial features remains difficult. Besides, spectrum extraction requires regions with large statistics while maps in energy bands allow only qualitative interpretation. The two main competing mechanisms in the VHE domain are the Inverse-Compton emission from accelerated electrons radiating through synchrotron in the X-ray domain and the interactions between accelerated hadrons and the surrounding medium, leading to the production and subsequent decay of {pi}{sup 0} mesons. The spectrum of the VHE emission from leptons is predicted to steepen with increasing distance from the acceleration zone, owing to synchrotron losses (i.e. cooled population). It would remain approximately constant for hadrons.Ideally, spectro-imaging analysis would have the same spatial scale in the TeV and X-ray domains, to distinguish the local emission mechanisms. More realistically, we investigate here the possibility of improving upon the currently published HESS results by using more sophisticated tools.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89025300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Simultaneous H.E.S.S. and Chandra observations of Sagittarius A* during an X-ray flare 在x射线耀斑期间，H.E.S.S.和钱德拉同时观测到人马座A*
arXiv: Astrophysics Pub Date : 2008-12-19 DOI: 10.1051/0004-6361:200810912
H. C. Aharonian, E. al.
{"title":"Simultaneous H.E.S.S. and Chandra observations of Sagittarius A* during an X-ray flare","authors":"H. C. Aharonian, E. al.","doi":"10.1051/0004-6361:200810912","DOIUrl":"https://doi.org/10.1051/0004-6361:200810912","url":null,"abstract":"The rapidly varying (~10 minute timescale) non-thermal X-ray emission observed from Sgr A* implies that particle acceleration is occuring close to the event horizon of the supermassive black hole. The TeV gamma-ray source HESS J1745-290 is coincident with Sgr A* and may be closely related to its X-ray emission. Simultaneous X-ray and TeV observations are required to elucidate the relationship between these objects. We report on joint H.E.S.S./Chandra observations performed in July 2005, during which an X-ray flare was detected. Despite a factor of 9 increase in the X-ray flux of Sgr A*, no evidence is found for an increase in the TeV gamma-ray flux from this region. We find that an increase in the gamma-ray flux of a factor of 2 or greater can be excluded at a confidence level of 99%. This finding disfavours scenarios in which the keV and TeV emission are associated with the same population of accelerated particles and in which the bulk of the gamma-ray emission is produced within ~10^{14} cm (~100 R_S) of the supermassive black hole.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81113312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 3
Motivations for Imaging Spectroscopy at Dome C 穹顶C成像光谱学的动机
arXiv: Astrophysics Pub Date : 2008-12-19 DOI: 10.1051/eas:0833033
A. Kelz
{"title":"Motivations for Imaging Spectroscopy at Dome C","authors":"A. Kelz","doi":"10.1051/eas:0833033","DOIUrl":"https://doi.org/10.1051/eas:0833033","url":null,"abstract":"Antarctica offers unique conditions for ground-based observations, such as low sky background in the infrared, improved seeing, and low turbulence and scintillation noise. These properties are particularly beneficial to imaging, precision photometry, and infrared observations. It may be less clear if Antarctica offers equally compelling advantages for spectroscopy, in particular in the optical domain. However, scientific programmes that make use of imaging (or 3D) spectroscopy for selected follow-up studies of IR surveys, long-term monitoring of extended targets and resolved stellar population studies in crowded fields, also benefit from the site conditions at Dome C.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84878412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
On the release of binding energy and accretion power in core collapse‐like environments 类核坍缩环境中结合能和吸积力的释放
arXiv: Astrophysics Pub Date : 2008-12-19 DOI: 10.1063/1.3682947
A. Socrates, E. Ramirez-Ruiz
{"title":"On the release of binding energy and accretion power in core collapse‐like environments","authors":"A. Socrates, E. Ramirez-Ruiz","doi":"10.1063/1.3682947","DOIUrl":"https://doi.org/10.1063/1.3682947","url":null,"abstract":"All accretion models of gamma‐ray bursts share a common assumption: accretion power and gravitational binding energy is released and then dissipated locally, with the mass of its origin. This is equivalent to the Shakura‐Sunyaev 1973 (SS73) prescription for the dissipation of accretion power and subsequent conversion into radiate output. Since their seminal paper, broadband observations of quasars and black hole X‐ray binaries insist that the SS73 prescription cannot wholly describe their behavior. In particular, optically thick black hole accretion flows are almost universally accompanied by coronae whose relative power by far exceeds anything seen in studies of stellar chromospheric and coronal activity. In this note, we briefly discuss the possible repercussions of freeing accretion models of GRBs from the SS73 prescription. Our main conclusion is that the efficiency of converting gravitational binding energy into a GRB power can be increased by an order of magnitude or more.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80328969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
The ultracool field dwarfs luminosity function from the Canada‐France Brown Dwarf Survey 超冷场使加拿大-法国褐矮星调查的光度函数相形见绌
arXiv: Astrophysics Pub Date : 2008-12-19 DOI: 10.1063/1.3099171
C. Reylé, P. Delorme, X. Delfosse, T. Forveille, C. Willott, L. Albert, É. Artigau
{"title":"The ultracool field dwarfs luminosity function from the Canada‐France Brown Dwarf Survey","authors":"C. Reylé, P. Delorme, X. Delfosse, T. Forveille, C. Willott, L. Albert, É. Artigau","doi":"10.1063/1.3099171","DOIUrl":"https://doi.org/10.1063/1.3099171","url":null,"abstract":"The Canada‐France Brown Dwarf Survey is a wide field survey for cool brown dwarfs conducted with the MegaCam camera on the CFHT telescope. Our objectives are to find ultracool brown dwarfs and to constrain the field brown dwarf mass function from a large and homogeneous sample of L and T dwarfs. We identify candidates in CFHT/Megacam i’ and z’ images and follow them up with pointed NIR imaging on several telescopes. Our survey has to date found 50 T dwarfs candidates and 170 L or late M dwarf candidates drawn from a larger sample of 1300 candidates with typical ultracool dwarfs i’‐z’ colours, found in 900 square degrees. We currently have completed the NIR follow‐up on a large part of the survey for all candidates from the latest T dwarfs known to the late L color range. This allows us to build on a complete and well defined sample of ultracool dwarfs to investigate the luminosity function of field L and T dwarfs.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76164770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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